// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_WM_CORE_IMAGE_GRID_H_
#define UI_WM_CORE_IMAGE_GRID_H_

#include "base/macros.h"
#include "base/memory/scoped_ptr.h"
#include "ui/compositor/layer.h"
#include "ui/compositor/layer_delegate.h"
#include "ui/gfx/geometry/rect.h"
#include "ui/gfx/geometry/size.h"
#include "ui/gfx/image/image_skia.h"
#include "ui/wm/wm_export.h"

namespace gfx {
class Image;
} // namespace gfx

namespace wm {

// An ImageGrid is a 3x3 array of ui::Layers, each containing an image.
//
// As the grid is resized, its images fill the requested space:
// - corner images are not scaled
// - top and bottom images are scaled horizontally
// - left and right images are scaled vertically
// - the center image is scaled in both directions
//
// If one of the non-center images is smaller than the largest images in its
// row or column, it will be aligned with the outside of the grid.  For
// example, given 4x4 top-left and top-right images and a 1x2 top images:
//
//   +--------+---------------------+--------+
//   |        |         top         |        |
//   | top-   +---------------------+  top-  +
//   | left   |                     | right  |
//   +----+---+                     +---+----+
//   |    |                             |    |
//   ...
//
// This may seem odd at first, but it lets ImageGrid be used to draw shadows
// with curved corners that extend inwards beyond a window's borders.  In the
// below example, the top-left corner image is overlaid on top of the window's
// top-left corner:
//
//   +---------+-----------------------
//   |    ..xxx|XXXXXXXXXXXXXXXXXX
//   |  .xXXXXX|XXXXXXXXXXXXXXXXXX_____
//   | .xXX    |                    ^ window's top edge
//   | .xXX    |
//   +---------+
//   | xXX|
//   | xXX|< window's left edge
//   | xXX|
//   ...
//
class WM_EXPORT ImageGrid {
public:
    // Helper class for use by tests.
    class WM_EXPORT TestAPI {
    public:
        explicit TestAPI(ImageGrid* grid)
            : grid_(grid)
        {
        }

        gfx::Rect top_left_clip_rect() const
        {
            return grid_->top_left_painter_->clip_rect_;
        }
        gfx::Rect top_right_clip_rect() const
        {
            return grid_->top_right_painter_->clip_rect_;
        }
        gfx::Rect bottom_left_clip_rect() const
        {
            return grid_->bottom_left_painter_->clip_rect_;
        }
        gfx::Rect bottom_right_clip_rect() const
        {
            return grid_->bottom_right_painter_->clip_rect_;
        }

        // Returns |layer|'s bounds after applying the layer's current transform.
        gfx::RectF GetTransformedLayerBounds(const ui::Layer& layer);

    private:
        ImageGrid* grid_; // not owned

        DISALLOW_COPY_AND_ASSIGN(TestAPI);
    };

    ImageGrid();
    ~ImageGrid();

    ui::Layer* layer() { return layer_.get(); }
    int top_image_height() const { return top_image_height_; }
    int bottom_image_height() const { return bottom_image_height_; }
    int left_image_width() const { return left_image_width_; }
    int right_image_width() const { return right_image_width_; }

    // Visible to allow independent layer animations and for testing.
    ui::Layer* top_left_layer() const { return top_left_layer_.get(); }
    ui::Layer* top_layer() const { return top_layer_.get(); }
    ui::Layer* top_right_layer() const { return top_right_layer_.get(); }
    ui::Layer* left_layer() const { return left_layer_.get(); }
    ui::Layer* center_layer() const { return center_layer_.get(); }
    ui::Layer* right_layer() const { return right_layer_.get(); }
    ui::Layer* bottom_left_layer() const { return bottom_left_layer_.get(); }
    ui::Layer* bottom_layer() const { return bottom_layer_.get(); }
    ui::Layer* bottom_right_layer() const { return bottom_right_layer_.get(); }

    // Sets the grid to display the passed-in images (any of which can be NULL).
    // Ownership of the images remains with the caller.  May be called more than
    // once to switch images.
    void SetImages(const gfx::Image* top_left_image,
        const gfx::Image* top_image,
        const gfx::Image* top_right_image,
        const gfx::Image* left_image,
        const gfx::Image* center_image,
        const gfx::Image* right_image,
        const gfx::Image* bottom_left_image,
        const gfx::Image* bottom_image,
        const gfx::Image* bottom_right_image);

    void SetSize(const gfx::Size& size);

    // Sets the grid to a position and size such that the inner edges of the top,
    // bottom, left and right images will be flush with |content_bounds_in_dip|.
    void SetContentBounds(const gfx::Rect& content_bounds_in_dip);

private:
    // Delegate responsible for painting a specific image on a layer.
    class ImagePainter : public ui::LayerDelegate {
    public:
        explicit ImagePainter(const gfx::ImageSkia& image)
            : image_(image)
        {
        }
        ~ImagePainter() override { }

        // Clips |layer| to |clip_rect|.  Triggers a repaint if the clipping
        // rectangle has changed.  An empty rectangle disables clipping.
        void SetClipRect(const gfx::Rect& clip_rect, ui::Layer* layer);

        // ui::LayerDelegate implementation:
        void OnPaintLayer(const ui::PaintContext& context) override;
        void OnDelegatedFrameDamage(const gfx::Rect& damage_rect_in_dip) override;
        void OnDeviceScaleFactorChanged(float device_scale_factor) override;
        base::Closure PrepareForLayerBoundsChange() override;

    private:
        friend class TestAPI;

        const gfx::ImageSkia image_;

        gfx::Rect clip_rect_;

        DISALLOW_COPY_AND_ASSIGN(ImagePainter);
    };

    enum ImageType {
        HORIZONTAL,
        VERTICAL,
        NONE,
    };

    // Sets |layer_ptr| and |painter_ptr| to display |image| and adds the
    // passed-in layer to |layer_|.  If image is NULL resets |layer_ptr| and
    // |painter_ptr| and removes any existing layer from |layer_|.
    // If |type| is either HORIZONTAL or VERTICAL, it may resize the image to
    // guarantee that it has minimum size in order for scaling work properly
    // with fractional device scale factors. crbug.com/376519.
    void SetImage(const gfx::Image* image,
        scoped_ptr<ui::Layer>* layer_ptr,
        scoped_ptr<ImagePainter>* painter_ptr,
        ImageType type);

    // Layer that contains all of the image layers.
    scoped_ptr<ui::Layer> layer_;

    // The grid's dimensions.
    gfx::Size size_;

    // Heights and widths of the images displayed by |top_layer_|,
    // |bottom_layer_|, |left_layer_|, and |right_layer_|.
    int top_image_height_;
    int bottom_image_height_;
    int left_image_width_;
    int right_image_width_;

    // Heights of the tallest images in the top and bottom rows and the widest
    // images in the left and right columns.  Note that we may have less actual
    // space than this available if the images are large and |size_| is small.
    int base_top_row_height_;
    int base_bottom_row_height_;
    int base_left_column_width_;
    int base_right_column_width_;

    // Layers used to display the various images.  Children of |layer_|.
    // Positions for which no images were supplied are NULL.
    scoped_ptr<ui::Layer> top_left_layer_;
    scoped_ptr<ui::Layer> top_layer_;
    scoped_ptr<ui::Layer> top_right_layer_;
    scoped_ptr<ui::Layer> left_layer_;
    scoped_ptr<ui::Layer> center_layer_;
    scoped_ptr<ui::Layer> right_layer_;
    scoped_ptr<ui::Layer> bottom_left_layer_;
    scoped_ptr<ui::Layer> bottom_layer_;
    scoped_ptr<ui::Layer> bottom_right_layer_;

    // Delegates responsible for painting the above layers.
    // Positions for which no images were supplied are NULL.
    scoped_ptr<ImagePainter> top_left_painter_;
    scoped_ptr<ImagePainter> top_painter_;
    scoped_ptr<ImagePainter> top_right_painter_;
    scoped_ptr<ImagePainter> left_painter_;
    scoped_ptr<ImagePainter> center_painter_;
    scoped_ptr<ImagePainter> right_painter_;
    scoped_ptr<ImagePainter> bottom_left_painter_;
    scoped_ptr<ImagePainter> bottom_painter_;
    scoped_ptr<ImagePainter> bottom_right_painter_;

    DISALLOW_COPY_AND_ASSIGN(ImageGrid);
};

} // namespace wm

#endif // UI_WM_CORE_IMAGE_GRID_H_
